Swapping the H190 Input Flange for 521

[wayno]

So Wayno, just wondering, did you ever try putting on the 521 input flange onto the LSD? what occurred to you to use a 620 flange?

I put the 620 flange in it because that was what was across the isle, a stock 620 I pulled the stock 620 pumpkin out just to put the LSD in to make sure it actually was an H190 LSD, I didn't believe it was one for quite a while, but after the 620 axle slid into it while it was in the 620 housing, then I believed.

So that is what was there, and I knew that flange would work with my driveline, but I didn't know it would work for sure till it did work without leaking in my truck.

As far as I know the 620 and 521 pinion flanges are the same flanges, but that might depend on the year, I don't recall what year the 620 was, it may have been a steel pumpkin while the 521 trucks had alloy pumpkins. like I said, I just pulled them both and looked at them side by side, the yoke part that slid into the front of the pumpkins looked the same, even though the flange that the driveline connected to did not look the same.

This LSD was in a 1993 hardbody, I thought the hardbody had a different rear axle other than the H190 by then, the door tag said HF35 which doesn't sound like an H190 to me, so that is why I spent the time removing the 620 pumpkin and installing the hardbody LSD pumpkin into the 620 rearend and sliding the axle in, I want to make sure it was an H190 LSD before I bought it, as I said before, there was no LSD tag on the axle housing.

[wayno]

You know that all them flanges are likely the same on H190 pumpkins/drop out gearsets, the 720 has the same ones as the 620, you just need to decide what style of flange you want, the earlier ones are not as beefy as the late ones, but they all had the same bolt pattern for the driveline till the C200 came out in the late 4X4 720 trucks, after that things started changing.

Just for fun I took my very early 1966 Datsun 520 driveline and bolted it to my extra 1985/86 Nissan C200 dually axle flange, it has the same bolt mount pattern as the 1966 driveline even though the dually flange(round and thick) doesn't look anything like the early 66 flange(thin and square), I personally would look for any later 620/720 H190 flange from a steel drop out pumpkin housing.

When you start moving parts around you can have issues, as I said I might have got lucky that my 620 pinion flange didn't leak when I filled the hardbody LSD unit with LSD gear oil, or maybe luck had nothing to do with anything as they are the same part except for the flange having a different pattern to bolt the driveline on in the later years after the 2wd 720, I don't know what year it changed on the 2wd trucks, and I definitely don't know a lot about the LSD units/lockers except what I have been told by others that I believe may know more than I do.

The 521 pinion flange may be the same also, you just have to pull both the flanges out of the units/gearsets and look at them very closely, are they the same size/length, do they look like they insert into the gearset the same distance when the nut is tightened, I made an educated guess and appear to have been right, but it was a guess, nothing more than a guess from looking at them side by side in the wrecking yard, I did likely have a tape measure with me, but I don't remember, that was a long time ago.